1. Field of the Invention
The present invention relates to an exhaust gas cooling device which cools exhaust gas from an internal combustion engine mounted on a vehicle through heat exchange between the exhaust gas and a coolant. More specifically, the present invention relates to an Exhaust Gas Recirculation (EGR) cooler.
2. Description of the Related Art
Technologies for preventing corrosion of components of an exhaust gas cooling device, such as an EGR cooler, caused by condensed water are conventionally known.
For example, an EGR device in which the bottom of the shell of an EGR cooler is inclined at an angle θ (at least 5°) so that the exhaust gas inlet side of the EGR cooler is lower than the other side is disclosed (refer to Japanese Patent Application Publication No. 2003-328863 (JP 2003-328863 A)). According to the EGR device, the condensed water which is generated in the exhaust gas flows smoothly from the exhaust gas outlet side to the exhaust gas inlet side, and harmful sulfuric acid in the condensed water is decomposed and vaporized by the high-temperature exhaust gas. Thus, the EGR cooler, EGR piping or EGR valve are unlikely to be corroded.
However, in the EGR device that is disclosed in JP 2003-328863 A, tubes through which the exhaust gas flows are secured to header plates with their both ends extending through the header plates (refer to paragraph [0005] of JP 2003-328863 A). Thus, condensed water may accumulate along the side surfaces of the header plates between the outer peripheral surfaces of the tubes that protrude from the header plates (refer to FIG. 9A).
When condensed water accumulates as described above, the tubes or the header plate may be corroded by the condensed water.